Change in structure or amount of an organisms genetic material Change in genotype produces change in phenotype mutant 2 types of mutation Chromosome mutation Change in structure of one chromosome ID: 1043315
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1. MutationHigher Biology
2. MutationChange in structure or amount of an organism’s genetic materialChange in genotype produces change in phenotype = mutant2 types of mutationChromosome mutationChange in structure of one chromosome
3. Chromosome mutationsChange in chromosome numberNon-disjunction in meiosisNon-disjunction of sex chromosomesComplete non-disjunction and polyploidy
4. Non-disjunction during meiosisSpindle fibre fails during meiosisMembers of one pair of homologous chromosomes fail to become separated2 gametes receive extra copy of affected chromosome2 gametes lack that chromosome
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6. Down’s SyndromeNon-disjunction in chromosome 21Occurs in human egg mother cellOne or more abnormal eggs formed (n = 24)Fertilised by normal sperm (n = 23)Formation of abnormal zygote (2n = 47)
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9. Non dis-junction of sex chromosomes
10. Turner’s syndromeGamete with no sex chromosomes fuses with normal X gameteZygote has chromosome complement 2n = 45Individuals are female and short in statureInfertile because ovaries haven’t developed normally
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12. Klinefelter’s syndromeXX egg fertilised by normal Y sperm orNormal X egg is fertilised by an XY spermZygote has chromosome complement 2n = 47 (44 + XXY)
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14. Always maleNormally infertile Cannot produce sperm
15. Complete non-disjunction and polyploidyAll the spindle fibres in a gamete mother cell failAll homologous pairs fail to become separatedProduction of abnormal diploid gametesEach contains 2 complete sets of chromosomes instead of one
16. PolyploidyFertilisation of abnormal gametesFormation of mutant plants which possess complete extra sets of chromosomesThis type of chromosome mutation is called polyploidy
17. A: the strawberry plant is exposed to a chemical B: due to the effect of chemical, total non-disjunction at meiosis produces diploid gametes(2n)C: two diploid gametes fuse at fertilisationD: a new plant develops which has four sets of chromosomes (4n)
18. Economic significancePolyploid plants are larger than diploid relativesIncreased seed and fruit sizeMany commercially developed crop plants are polyploid -apples -strawberries -tomatoes -wheatGive greater yields
19. Effects of polyploidyUneven sets of chromosome -polyploidy plants are sterileProduce seedless fruitIncrease in vigourResistance to disease
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